If you have still got the original Wilson leather grip on your K90,you might want to order a Tennis Warehouse leather grip and replace it with that one.
The Wilson leather,to my knowledge, is 1,8mm thick, whereas the TW leather can be purchased in 1,3mm.

I tried this myself on my 2 racquets and it worked a treat.
Maybe the 0,5 mm will do the trick!
(Tipp:Try and pull the leather as much as you can while re-gripping, and pay attention not to overlap too much)

If you have still got the original Wilson leather grip on your K90,you might want to order a Tennis Warehouse leather grip and replace it with that one.
The Wilson leather,to my knowledge, is 1,8mm thick, whereas the TW leather can be purchased in 1,3mm.

What other option do you have? Apply and have a hit with it, you could also use thinner overgrips (assuming you use them.)

Failing that I've heard that good customisation services such as RPNY and P1 (possibly other less know customisers) can shave the handle down a grip size maintaining the grip shape and adding lead to compensate for lost weight (which shouldn't be too much at all.)

Good luck!

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Dunlop Bio Max 200G | 336g | 32.0cm
Better to remain silent and be thought a fool than to speak out and remove all doubt.